Add clang-tidy support

For every file which we can run clang-tidy (C/C++ clang-built), we add a
new build node that depends on the object file (since clang-tidy does
not export a depfile), and is depended on by the link step. This is
better than how we're doing it in make, since calling tidy can be turned
on or off without needing to rebuild the object files.

This does not attempt to port WITH_TIDY_ONLY from Make, since the way
that it works is broken (due to the lack of a depfile).

Bug: 32244182
Test: WITH_TIDY=true mmma -j bionic/libc
Test: ./soong (Setting ClangTidy: true)
Change-Id: I40bbb5bb00d292d72bf1c293b93080b5f9f6d8ea

cc/builder.go

@@ -150,6 +150,14 @@ var (
 			Restat:      true,
 		},
 		"crossCompile")
+
+	clangTidy = pctx.AndroidStaticRule("clangTidy",
+		blueprint.RuleParams{
+			Command:     "rm -f $out && ${config.ClangBin}/clang-tidy $tidyFlags $in -- $cFlags && touch $out",
+			CommandDeps: []string{"${config.ClangBin}/clang-tidy"},
+			Description: "tidy $out",
+		},
+		"cFlags", "tidyFlags")
 )
 
 func init() {
@@ -174,8 +182,10 @@ type builderFlags struct {
 	libFlags    string
 	yaccFlags   string
 	protoFlags  string
+	tidyFlags   string
 	toolchain   config.Toolchain
 	clang       bool
+	tidy        bool
 
 	stripKeepSymbols       bool
 	stripKeepMiniDebugInfo bool
@@ -183,18 +193,21 @@ type builderFlags struct {
 }
 
 type Objects struct {
-	objFiles android.Paths
+	objFiles  android.Paths
+	tidyFiles android.Paths
 }
 
 func (a Objects) Copy() Objects {
 	return Objects{
-		objFiles: append(android.Paths{}, a.objFiles...),
+		objFiles:  append(android.Paths{}, a.objFiles...),
+		tidyFiles: append(android.Paths{}, a.tidyFiles...),
 	}
 }
 
 func (a Objects) Append(b Objects) Objects {
 	return Objects{
-		objFiles: append(a.objFiles, b.objFiles...),
+		objFiles:  append(a.objFiles, b.objFiles...),
+		tidyFiles: append(a.tidyFiles, b.tidyFiles...),
 	}
 }
 
@@ -203,6 +216,10 @@ func TransformSourceToObj(ctx android.ModuleContext, subdir string, srcFiles and
 	flags builderFlags, deps android.Paths) Objects {
 
 	objFiles := make(android.Paths, len(srcFiles))
+	var tidyFiles android.Paths
+	if flags.tidy && flags.clang {
+		tidyFiles = make(android.Paths, 0, len(srcFiles))
+	}
 
 	cflags := flags.globalFlags + " " + flags.cFlags + " " + flags.conlyFlags
 	cppflags := flags.globalFlags + " " + flags.cFlags + " " + flags.cppFlags
@@ -223,11 +240,13 @@ func TransformSourceToObj(ctx android.ModuleContext, subdir string, srcFiles and
 
 		var moduleCflags string
 		var ccCmd string
+		tidy := flags.tidy && flags.clang
 
 		switch srcFile.Ext() {
 		case ".S", ".s":
 			ccCmd = "gcc"
 			moduleCflags = asflags
+			tidy = false
 		case ".c":
 			ccCmd = "gcc"
 			moduleCflags = cflags
@@ -264,24 +283,45 @@ func TransformSourceToObj(ctx android.ModuleContext, subdir string, srcFiles and
 				"ccCmd":  ccCmd,
 			},
 		})
+
+		if tidy {
+			tidyFile := android.ObjPathWithExt(ctx, srcFile, subdir, "tidy")
+			tidyFiles = append(tidyFiles, tidyFile)
+
+			ctx.ModuleBuild(pctx, android.ModuleBuildParams{
+				Rule:   clangTidy,
+				Output: tidyFile,
+				Input:  srcFile,
+				// We must depend on objFile, since clang-tidy doesn't
+				// support exporting dependencies.
+				Implicit: objFile,
+				Args: map[string]string{
+					"cFlags":    moduleCflags,
+					"tidyFlags": flags.tidyFlags,
+				},
+			})
+		}
+
 	}
 
 	return Objects{
-		objFiles: objFiles,
+		objFiles:  objFiles,
+		tidyFiles: tidyFiles,
 	}
 }
 
 // Generate a rule for compiling multiple .o files to a static library (.a)
 func TransformObjToStaticLib(ctx android.ModuleContext, objFiles android.Paths,
-	flags builderFlags, outputFile android.ModuleOutPath) {
+	flags builderFlags, outputFile android.ModuleOutPath, deps android.Paths) {
 
 	arCmd := gccCmd(flags.toolchain, "ar")
 	arFlags := "crsPD"
 
 	ctx.ModuleBuild(pctx, android.ModuleBuildParams{
-		Rule:   ar,
-		Output: outputFile,
-		Inputs: objFiles,
+		Rule:      ar,
+		Output:    outputFile,
+		Inputs:    objFiles,
+		Implicits: deps,
 		Args: map[string]string{
 			"arFlags": arFlags,
 			"arCmd":   arCmd,
@@ -294,7 +334,7 @@ func TransformObjToStaticLib(ctx android.ModuleContext, objFiles android.Paths,
 // very small command line length limit, so we have to split the ar into multiple
 // steps, each appending to the previous one.
 func TransformDarwinObjToStaticLib(ctx android.ModuleContext, objFiles android.Paths,
-	flags builderFlags, outputPath android.ModuleOutPath) {
+	flags builderFlags, outputPath android.ModuleOutPath, deps android.Paths) {
 
 	arFlags := "cqs"
 
@@ -303,8 +343,9 @@ func TransformDarwinObjToStaticLib(ctx android.ModuleContext, objFiles android.P
 		dummyAr := android.PathForModuleOut(ctx, "dummy"+staticLibraryExtension)
 
 		ctx.ModuleBuild(pctx, android.ModuleBuildParams{
-			Rule:   emptyFile,
-			Output: dummy,
+			Rule:      emptyFile,
+			Output:    dummy,
+			Implicits: deps,
 		})
 
 		ctx.ModuleBuild(pctx, android.ModuleBuildParams{
@@ -347,9 +388,10 @@ func TransformDarwinObjToStaticLib(ctx android.ModuleContext, objFiles android.P
 
 		if in == "" {
 			ctx.Build(pctx, blueprint.BuildParams{
-				Rule:    darwinAr,
-				Outputs: []string{out},
-				Inputs:  l,
+				Rule:      darwinAr,
+				Outputs:   []string{out},
+				Inputs:    l,
+				Implicits: deps.Strings(),
 				Args: map[string]string{
 					"arFlags": arFlags,
 				},